This application claims the priority benefit of Taiwan application serial no. 89104136, filed Mar. 8, 2000.
1. Field of Invention
The present invention relates to a track seeking and track locking method in an optical storage device. More particularly, the present invention relates to a track seeking and track locking method that controls track error zero cross (TEZC) signal and radio frequency ripple zero cross (RFZC) signal for preventing state transition within a safety interval in an optical storage device.
2. Description of Related Art
Due to the rapid advance in data storage technologies, capacity-limited conventional magnetic disk storage system is gradually replaced by optical disk storage device, especially after rewritable optical storage devices are introduced.
For the track seeking and track locking processes in the conventional optical storage device, the sinusoidal or triangular track error (TE) signal and the radio frequency ripple (RFRP) signal has a phase difference of about 90xc2x0 (the TE signal of a DVD system is in triangular waveform). FIG. 1 is diagram showing the waveforms of TEZC and RFZC signals derived from the zero-crossing of the TE and RFRP signals. A complete high/low cycle of the TEZC signal indicates that an optical pick-up head jumps across one track. In general, the optical storage device utilizes the TEZC and RFZC signals to compute the number of tracks jumped by the optical pick-up head. In addition, the TEZC and RFZC signal can be utilized to control the jumping speed of the optical pick-up head.
FIG. 2 is a diagram showing the waveforms of TEZC and RFZC signals due to some distortion of the TE and RFRP signals. Because of some intrinsic problems of the TE and RFRP signals or some external interference, glitches are often generated leading to the formation of abnormal signal fluctuation. Consequently, the TEZC signal and the RFZC signal also contain a number of glitches. These glitches in the TEZC and RFZC signals are error signals that need to be removed or reduced. If these glitches remain in the TEZC or RFZC signals, an abnormal operation may occur in the optical storage device.
To resolve the xe2x80x98glitchxe2x80x99 issue, conventional method relies on referencing both the TEZC signal and the RFZC signal. Under this cross-referencing scheme, whenever a transition has occurred in one of the two signals, the other signal is checked to see if similar transition has also occurred. For example, if there is a state transition of the TEZC signal, another state transition of the TEZC signal is impossible until a state transition of the RFZC signal occurs. Similarly, if there is a state transition of the RFZC signal, another state transition of the RFZC signal is impossible until a state transition of the TEZC signal occurs.
FIG. 3 is a diagram showing the glitch-contained TEZC and RFZC signal waveform and their de-glitch DTEZC and DRFZC signal waveform after mutual referencing.
Despite the capacity for removing glitches contained in the TEZC and RFZC signal, the conventional solution of mutual referencing has some drawbacks, including: (1) When a glitch is simultaneously produced in the TEZC signal and the RFZC signal, the glitch remains; (2) If state transition of either the TEZC signal or the RFZC signal does not occur, neither does the state transition of the TEZC signal or the RFZC signal; (3) The glitch signal often leads to a change in duty cycle; (4) The relationship of a 90xc2x0 phase angle difference between the TE signal and the RFRP signal is gradually changed when operating at a high operating speed, and the signals cannot be corrected when the signals are dangerously close together.
Accordingly, one object of the present invention is to provide a track seeking and track locking method capable of keeping the TEZC signal and the RFZC signal unchanged within a computed interval.
A second object of this invention is to provide a track seeking and track locking method capable of preventing the interference of the TEZC and the RFZC signal by glitches, thereby reducing track errors and speed computational errors.
To achieve these and other advantages in accordance with the purpose of the invention, as embodied and broadly described herein, the invention provides a track seeking and track locking method. De-glitch track error zero cross (DTEZC) signal is provided. When the DTEZC signal undergoes a state transition, a first safety time interval and a second safety time interval are generated. In addition, de-glitch radio frequency zero cross (DRFZC) signal is provided. When the DRFZC signal undergoes a state transition, a third safety time interval and a fourth safety time interval are generated. As soon as TEZC signal undergoes a state transition, the DTEZC signal also undergoes a state transition. However, the DTEZC signal will not follow any state transition of the TEZC signal within the first safety time interval and the third safety time interval. Yet, outside the first safety time interval and the third safety time interval, the DTEZC signal and the TEZC signal are in identical state. Similarly, as soon as RFZC signal undergoes a state transition, the DRFZC signal also undergoes a state transition. However, the DRFZC signal will not follow any state transition of the RFZC signal within the second safety time interval and the fourth safety time interval. Yet, outside the second safety time interval and the fourth safety time interval, the DRFZC signal and the RFZC signal are in identical state.
The invention further provides a track seeking and track locking method in an optical storage device. It first provides a first track-cross signal and a second track-cross signals, wherein a phase difference exists between the first and the second track-cross signals. A first and a second protection windows are then set in response to a state change in the first track-cross signal, and a third and a fourth protection windows are set in response to a state change in the second track-cross signal. A third and a fourth track-cross signals are generated according to the first and the second track-cross signals, and the first, the second, the third and the fourth protection windows. During the first and the third protection windows, the state of the third track-cross signal keeps; otherwise, the third track-cross signal is related to the first track-cross signal. Meanwhile, during the second and the fourth protection windows, the state of the fourth track-cross signals keeps; otherwise, the fourth track-cross signal is related to the second track-cross signal.
It is to be understood that both the foregoing general description and the following detailed description are exemplary, and are intended to provide further explanation of the invention as claimed.